Acoustical insulation is well known in the art. Acoustical insulation typically relies upon both sound absorption, i.e. the ability to absorb incident sound waves, and transmission loss, i.e. the ability to reflect incident sound waves, in order to provide sound attenuation. One of the more prevalent uses of such insulation is in the motorized vehicle field where engine compartments, fire walls, fender wells, doors, floor pans and other components of the passenger compartment shell are commonly acoustically insulated to reduce engine and road noise for the benefit and comfort of passengers.
In the automotive undercarpet industry, it is important to prevent compression of the carpet surrounding the area on which a load, i.e., a passenger's feet, is placed. By preventing compression, acoustical and insulative properties to be maintained. Various methods of manufacturing or fabricating acoustical and thermal insulators are known in the art. Typically, an automotive carpet is placed over a cotton shoddy or a uniform polymer based mat. These undercarpets are typically produced by carding, garnetting or air laid systems known in the art. Examples of other methods and products are found in U.S. Pat. No. 5,266,374, and U.S. publication Nos. 2003/0066708 A1 and 2003/0096079.
U.S. Pat. No. 5,266,374 teaches a carpet for vehicles that prevents the transmission of sound and vibration into a vehicle cabin. '374 teaches a rigid polyurethane sheet laid on a metal panel, such as that of a vehicle floor. The polyurethane sheet comprises an elastomeric rubber layer, which further comprises a plurality of incompressible, square blocks which are intermittently disposed between the rigid and elastomeric layers. The rigid blocks are arranged so as to not come into contact with one another.
U.S. Pub. No. 2003/0096079 A1 teach a sound attenuating laminate for use in vehicles including a substrate having opposite first and second surfaces formed of foam, massback, thermoformable fibrous material. A first surface is attached to a vehicle panel. A non-porous polyurethane layer is applied to either portions of or the entire substrate second surface. The laminate is formed by forming the substrate in the shape of the article to which it is to be applied and then spraying the polyurethane layer onto the substrate.
U.S. Pub. No. 2003/0066708 A1 teach a sound attenuating composite article for vehicles having several layers of material. The first layer is either fiber batting or acoustic foam, the second layer is a thermoplastic material fused to the surface of the first layer, the third layer is a thermoplastic material fused to the surface of the second layer, and the forth layer is a woven or nonwoven mixture of fibers attached to the third layer of material. The article is formed by providing the first layer and then extruding a second layer of thermoplastic material onto the first layer, compressing the first and second layers and then extruding a third layer of thermoplastic material onto the second layer. Scrim material is then attached to the third layer of thermoplastic material and then all four layers are compressed via nip rolls. Finally, the article is place in a heated mold and heated via infrared radiation.
In many acoustical insulation applications and particularly those relating to motorized vehicles, high compressive strength is advantageous, especially in vehicle carpet applications so that the acoustical properties are maintained. As demonstrated by these prior art patents, it has generally been found necessary to coat a uniform substrate with one or more layers of thermoplastic material. A need is therefore identified for an improved insulation providing enhanced acoustical properties while also exhibiting compression-recovery. There is also a need for a product that can be manufactured at a lower cost and reduces waste.